Method of operating a hybrid burner

ABSTRACT

The process relates to the operation of a hybrid burner. The hybrid burner has a premix burner and a pilot burner. The premix burner includes a premix air supply duct, into which a premix fuel supply duct opens. The pilot burner includes an air supply duct and a fuel supply duct for liquid and/or gaseous fuel. When the hybrid burner is in operation, air is supplied through the air supply duct and through the premix air supply duct, oil is supplied through the fuel supply duct and water is supplied through the premix fuel supply duct.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of copending International Application PCT/DE99/02495, filed Aug. 10, 1999, which designated the United States.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an operating method for a hybrid burner, which has a premix burner and a pilot burner. The premix burner has a premix air supply duct and at least one premix fuel supply duct which opens into the premix air supply duct. The pilot burner has an air supply duct and a fuel supply duct for liquid and/or gaseous fuel.

[0004] A hybrid burner is known from commonly assigned U.S. Pat. No. 5,451,160 (see European patent EP 0 580 683 B1), entitled Burner Configuration, Particularly for Gas Turbines, For the Low-Pollutant Combustion of Coal Gas and Other Fuels. The hybrid burner has a pilot burner system which is concentrically surrounded by a premix burner. The pilot burner system has a central oil supply with an inner gas supply duct arranged around it. The gas supply duct is surrounded by a concentrically arranged inner air supply duct. The pilot burner system is in turn surrounded by a supply duct system for various fuels, this supply duct system having a first gas supply duct and a second gas supply duct and an oil supply duct. An outer air supply duct surrounds the supply duct system for the fuels, the ducts of this supply duct system respectively opening into the outer air supply duct. The outer air supply duct and the supply duct system for the fuels form the premix burner of the hybrid burner.

[0005] The hybrid burner can be operated in various modes of operation, air for a combustion process being supplied by way of the outer and the inner air supply ducts and fuel for the combustion process being supplied by way of one or more of the ducts used for the fuel supply. In these modes of operation, a first diffusion mode is known in which coal gas is supplied to the combustion by means of the first gas supply duct of the pilot burner, coal gas is likewise supplied by means of the second gas supply duct of the premix burner and air being is supplied by means of both the air supply ducts. In a second diffusion mode of operation, fuel and air are supplied as in the first diffusion mode of operation and, in addition, water vapor is supplied by means of the first gas supply duct. In a third diffusion mode of operation, fuel and air are supplied as in the first diffusion mode of operation and, in addition, water is supplied by means of the oil supply duct.

SUMMARY OF THE INVENTION

[0006] It is accordingly an object of the invention to provide a method of operating a hybrid burner, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a hybrid burner to be operated with reduced NO_(x) output.

[0007] With the foregoing and other objects in view there is provided, in accordance with the invention, a method of operating a hybrid burner having a premix burner and a pilot burner, the premix burner having a premix air supply duct and a premix fuel supply duct configured for supplying oil and opening into the premix air supply duct, and the pilot burner having an air supply duct and a fuel supply duct for liquid and/or gaseous fuel; and supplying air by way of the air supply duct and by way of the

[0008] premix air supply duct, supplying oil by way of the fuel supply duct, and supplying water by way of the premix fuel supply duct configured to supply oil.

[0009] In accordance with an added feature of the invention, the water is supplied in liquid phase.

[0010] According to the invention, the object is achieved by a method as described in the preamble to claim 1, in which air is supplied to a combustion process by means of the air supply duct and by means of the premix air supply duct, oil is supplied to the combustion process by means of the fuel supply duct and water is supplied to the combustion process by means of the premix fuel supply duct designed to supply oil.

[0011] The invention is based on the knowledge that during the operating of the hybrid burner in the second or third diffusion mode of operation, as described in the above-mentioned U.S. Pat. No. 5,451,160 (EP 0 580 683 B1), the excitation of so-called combustion chamber vibrations can be promoted if the quantity of water vapor supplied per unit time exceeds a water vapor limiting value, or the quantity of water supplied per unit time exceeds a water limiting value. Combustion chamber vibrations are understood to mean stationary pressure vibrations forming in the combustion chamber during the operation of the hybrid burner. The combustion chamber vibrations can lead to a high level of mechanical loading on the parts of the gas turbine forming the combustion chamber. The invention is based on the further knowledge that the water limiting value and the water vapor limiting value depend on which duct of the hybrid burner is used for the supply of the water.

[0012] In a hybrid burner operated by the method according to the invention, the water is supplied by means of the premix fuel duct as liquid and/or as vapor. By this means, the water limiting value, or the water vapor limiting valve, can be very much higher than in the case of a hybrid burner which is operated according to the first or second diffusion operation as described in the above-mentioned U.S. Pat. No. 5,451,160 (EP 0 580 683 B1). The water supplied is used to reduce the NO_(x) during the combustion of fuel and air which has been supplied. The NO_(x) reduction rate becomes higher as the quantity of water supplied per unit time becomes greater. In the method according to the invention, as compared with a method according to the prior art, the quantity of water which can be supplied per unit time is very much greater and, in consequence, the NO_(x) emission is also reduced. In addition, the output of the hybrid burner can be higher for the same NO_(x) emission because, since it is possible to supply a larger quantity of water, the quantity of fuel and air which can be burned per unit time can be correspondingly greater.

[0013] With the above and other objects in view there is also provided, in accordance with the invention, a method of operating a hybrid burner of the type having a premix burner and a pilot burner, the premix burner having a premix air supply duct and a premix fuel supply duct opening into the premix air supply duct, and the pilot burner having an air supply duct and a fuel supply duct for liquid and/or gaseous fuel, the method which comprises:

[0014] supplying air by way of the air supply duct and by way of the premix air supply duct, supplying fuel gas exclusively by way of the fuel supply duct, and supplying water by way of the premix fuel supply duct.

[0015] Here, therefore, the air is supplied by means of the air supply duct and by means of the premix air supply duct, fuel gas is exclusively supplied by means of the fuel supply duct and water is supplied by means of the premix fuel supply duct.

[0016] In this method also, the supply of a larger quantity of water is possible without any significant excitation of combustion chamber vibrations occurring. By this means, the NO_(x) emission can be reduced for the same output of the hybrid burner. For the same NO_(x) emission, the output of the hybrid burner can likewise be increased.

[0017] Water is preferably supplied in the liquid state by means of the premix fuel supply duct which is designed for the supply of oil. Water vapor is again preferably supplied by means of a premix fuel supply duct which is designed for the supply of fuel gas. In consequence, the method can be applied to hybrid burners, or equivalent burner arrangements, which are available and already employed in the operation of a gas turbine. Equivalent burner arrangements are, for example, understood to mean such burner arrangements as have a premix burner and a pilot burner which are spatially separated from one another, their flames having a mutual influence on one another in operation.

[0018] Other features which are considered as characteristic for the invention are set forth in the appended claims.

[0019] Although the invention is illustrated and described herein as embodied in an operating method for a hybrid burner, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

[0020] The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0021] The sole figure of the drawing is diagrammatic illustration of a hybrid burner, not drawn to scale.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Referring now to the figure of the drawing in detail there is shown a hybrid burner 20 for a combustion chamber of a gas turbine (the latter is not illustrated in detail for purposes of clarity). The hybrid burner has a pilot burner 21 and a premix burner 22. The pilot burner 21 comprises a fuel supply duct 1 for liquid or gaseous fuel, a fuel gas supply duct 2 for gaseous fuel and an air supply duct 3. The premix burner 22 comprises a first premix fuel supply duct 8 and a second premix fuel supply duct 16, which are respectively embodied for the supply of fuel gas, a premix air supply duct 4 and a third premix fuel supply duct 12, which is embodied for the supply of liquid fuel. The fuel gas supply duct 2, the air supply duct 3, the first premix fuel supply duct 8, the second premix fuel supply duct 16, the premix air supply duct 4 and the third premix fuel supply duct 12 are respectively configured as annular ducts.

[0023] The fuel supply duct 1 is centrally arranged along a main axis 30. This fuel supply duct is surrounded by the fuel gas supply duct 2, which is in turn surrounded by the air supply duct 3. The air supply duct 3 has a mouth 31, which forms the mouth of the pilot burner.

[0024] Upstream of its mouth 31, the air supply duct 3 is surrounded by the third premix fuel supply duct 12. The air supply duct 3 is further surrounded by the first premix fuel supply duct 8, which is in turn surrounded by the second premix fuel supply duct 16. The pilot burner 21 and the premix fuel supply ducts 8, 12 and 16 are surrounded by the outer air supply duct 4. The third premix fuel supply duct 12 opens into the outer air supply duct 4. The first premix fuel supply duct 8 and the second premix fuel supply duct 16 open into the premix air supply duct 4 before the third premix fuel supply duct 12, viewed in the direction toward the mouth 31.

[0025] The hybrid burner 20 has a mouth 23, by means of which it opens into a combustion chamber 24 of a gas turbine which is not illustrated in detail, but which is indicated by the cutoff line just below the mouth 23 of the hybrid burner 20.

[0026] During a diffusion operation of the hybrid burner, air is respectively supplied by way of the air supply duct 3 and by way of the premix air supply duct 4, oil is supplied by way of the fuel supply duct 1, and water is supplied by way of the third premix supply duct 12. All these supplies enter the combustion chamber 24 where the oil and the air are combusted in the presence of the water. In another diffusion operation, water vapor is supplied by way of the second premix fuel supply duct 8 instead of, or at the same time as, the supply of water by means of the third premix fuel supply duct 12.

[0027] The hybrid burner 20 can also be operated in a so-called gas diffusion operation, gaseous fuel being supplied exclusively by means of the fuel supply duct 1 or the fuel gas supply duct 2, air by means of the air supply duct 3 or the premix air supply duct 4 and water by means of the premix air supply duct 8, 12 and/or 16.

[0028] In the case of gas diffusion operation, the supply of water vapor takes place by means of the second premix supply duct 8 and/or the supply of water by means of the third premix supply duct 12.

[0029] A common feature of all these operating methods is that a combustion of fuel and air can be carried out in the presence of a large quantity of water without the result that combustion vibrations are excited. In consequence, the quantity of the oxides of nitrogen formed during the combustion can be substantially reduced. The operating methods can be easily applied in existing hybrid burners. 

I claim:
 1. A method of operating a hybrid burner, which comprises: providing a hybrid burner with a premix burner and a pilot burner, the premix burner having a premix air supply duct and a premix fuel supply duct configured for supplying oil and opening into the premix air supply duct, and the pilot burner having an air supply duct and a fuel supply duct for liquid and/or gaseous fuel; and supplying air by way of the air supply duct and by way of the premix air supply duct, supplying oil by way of the fuel supply duct, and supplying water by way of the premix fuel supply duct configured to supply oil.
 2. The method according to claim 1 , which comprises supplying the water in liquid phase.
 3. A method of operating a hybrid burner of the type having a premix burner and a pilot burner, the premix burner having a premix air supply duct and a premix fuel supply duct opening into the premix air supply duct, and the pilot burner having an air supply duct and a fuel supply duct for liquid and/or gaseous fuel, the method which comprises: supplying air by way of the air supply duct and by way of the premix air supply duct, supplying fuel gas exclusively by way of the fuel supply duct, and supplying water by way of the premix fuel supply duct.
 4. The method according to claim 3 , which comprises configuring the premix fuel supply duct for supplying fuel gas and supplying the water in water vapor phase by way of the premix fuel supply duct. 